Bertram 68 motoryacht repower

I'll be studying these pictures for a long time to come.
What clutch was used? I can see it had a down angle.
Big ole coach roof hatch works darn good.

Is this the boat that had 3412s originally planned?

Send in more pictures. Of the extension also please.

Thx
Ralph

Do you engine guys think the owner should have gone with larger displacement engines? Are those 12.9s going to be stressed pushing that boat at cruise speed? Maybe the owner just wants to cruise at idle speed.

No idea about if and how much oversized the original shafts were (or not) vs. the original power.
But the exhaust size depends more on displacement and rpm, rather than power.
And here we are talking of a 40% displacement increase, with the same max rated rpm...
Good luck with that.

20 kts at 1900 rpm with less than 80% load doesn't sound too bad, actually.
I guess that aiming at a much faster speed with that hull would be pointless.

Looks great ! Nice job. I wish you guys would wear some better footwear while working on those bilge monsters! Ouch!

Like my 58, those were low restriction 10 inch exhaust lines. From a old design 14L to a modern 13L may be a loss in engine displacement but doable. Those one piece 2.5 inch shafts with an extra strut should be around the safe max but doable well also.
The grace in added hull displacement, the beam to length ratio just improved big time. It is not unusual for speed increases with the same engines when cockpit extensions are added. I remember a 58 Bert that was lengthened to 80. Turned the same speed.
I do look forward to a 1000 hour report and I anticipate good news then.

LOVE threads that document refits. Thank you Trinimax!

One design item I question, moving the rudders back and not the props.
You will get no wash on the rudders and poor slow speed operation. I used to run a Roamer house boat with an extension, just the rudders moved back. Ended up upgrading to large stablizer fins for rudders. Still throttles and clutches needed in slow speed areas. The owner may consider moving back to the original locations.

You're forgetting that the switch was from detroits which exhaust on every stroke to 4 cycle so the volume of exhaust is actually less.

Doh! Don't ask me why, but when I wrote my previous comment I calculated by heart a displacement of around 9L for the V12 DD 71 - hence my comment on 40% increase.
Not sure of what I was thinking...

Looks good. I do not know, so I'm asking, That white exhaust elbow looks the same on the out side as on the inside? Or does it have a turning vane or defection point in it? Or does it just dump into the '' Tee''?
How does it work?

I think it is a T to allow room to keep water from surging up the exhaust and into the engine.

+ 1 on DeAngelo

How much weight was saved ?